1. Field of Invention
This invention relates to free-space micro-electro-mechanical system (MEMS) optical switches. In particular, it relates to mechanical angular alignment enhancement structures associated with free-rotating hinged micro-mirror switching elements.
2. Description of Related Art
As the demand for data-networking capacity has grown, managing optical networks at the coarse granularity of the wavelength level (OC-48 and beyond) has become increasingly critical. Optical crossconnects (OXCs) with high port-count--on the order of 1,000--are emerging as the chief candidates for achieving this end. This vision, however, imposes stringent requirements on the OXCs, chiefly in the areas of port-count and loss budget, that far outstrip available technology. Recently, free-space optical MEMS (micro-electro-mechanical systems) have begun to show promise for this application, due largely to the combined merits of free-space optics and integrated photonics.
Free-space MEMS optical switches aiming at large-scale switch fabrics have been demonstrated using various approaches. See, for example, (1) H. Toshiyoshi and H. Fujita, "Electrostatic Micro Torsion Mirrors for an Optical Switch Matrix," J. Microelectromechanical Systems, vol. 5, no. 4, pp. 231-237, 1996, (2) L. Y. Lin, E. L. Goldstein, and R. W. Tkach, "Free-space Micromachined Optical Switches for Optical Networking," IEEE J. Selected Topics in Quantum Electronics: Special Issue on Microoptoelectromechanical Systems (MOEMS), vol. 5, no. 1, pp. 4-9, 1999, (3) R. T. Chen, H. Nguyen, and M. C. Wu, "A Low Voltage Micromachined Optical Switch by Stress-induced Bending," in 12th IEEE International Conference on Micro Electro Mechanical Systems, Orlando, Fla., Jan. 17-21, 1999, and (4) B. Behin, K. Y. Lau, and R. S. Muller, "Magnetically Actuated Micromirrors for Fiber-optic Switching," in Solid-State Sensor and Actuator Workshop, Hilton Head Island, S.C., Jun. 8-11, 1998, each incorporated by reference herein in their entireties.
This work has rapidly revealed the intrinsically good optical quality of free-space interconnects, particularly in the areas of crosstalk, polarization- and waveleng thin dependence, and bit-rate transparency. The demonstrated switching times are also well suited for the applications of OXCs in core-transport networks.
However, the issue of tight optical-alignment tolerances in free-space optics remains to be solved.